Composition of matter and process of making the same.



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ALFRED J. LIEBILJIANN, 01' YORK, N, 1..

corrrosrrrou or trauma AND rnoonss or MAKING SAME.

No Drawing.

The object of my invention is to providea new composition of matter which may be used for many useful purposes, as for electrodes and brushes for dynainos and electric motors.

I have found that the metal tungsten when properly mixed with carbon or copper or both of them, produces a composition of patter which has great advantages for use in the electrical art, for the purposes above stated. Such a composition of matter is of excellent wearing quality and its use as a brush for electric machinery eliminates to a great degree the objectionable sparking and other troubles.

The modern art of producing tungsten metal has been so :far developed that it is possible to obtain tungsten metal either in the form of very fine and soft black powder or in the form of coarse, hard and grainy powder or in any of the intermediate forms.

I have discovered that the best brushes ii ill be obtained by a mixture of carbon and tungsten; or of carbon, copper and tungsten. is. great advantage arising from my composition is that it can be made with any proportions of material suited for thedspecial purpose for which it is desired. If the material-is to be used as a brush in a slow moving machine, less hardness is required, while if it is to be used for brush in a fast moving machine, a harder material is required.- The degrees of hardness of my composition of matter are regulated by thedcgrees of hardness and the proportions of the tungsten The finer the tungsten powder, the

softer it is, and the softer the composition of which it is a constituent. On the other hand, the coarser the grain of the tungsten powder, the harder it is, and the more hard ncss it gives to the composition. of material of which it 13 a constituent. In a machine which generates low currents, more tungsten could be used than in one which generates very high currents, because the conductivity of tungsten is not as high as copper and in Specification of Letters Patent.

iPatented Mar. 2%, 19116.

Application fiied March 12, 1915. ficrial 21013336.

the case of high currents, I have found it advisable to counter-balance this property of tungsten by an increased admixture of copper. As mentioned above, a very wide range for the manufacture of my invention is given by the innumerable difierent grades of hardness and size of grain which can be obtained of tungsten and the different proportions of its admixture. These qualities of tungsten allow a brush to be made of almost any hardness and with a very wide range of electrical conductivity.

In the carrying out of my invc ItiOH, while it is possible to simply take the carbon or graphite powder and mix it with tungsten powder, or tungsten and copper powder together and compress the mixture under a high pressure and then heat it in a vacuum, or an inert atmosphere to obtain a solid cake of the mixture, I have found it to be of great advantage to follow a more specific procedure.

I have obtained the very best results in mixing the carbon or graphite powder and powdered tungsten with an amalgam of copper, such amalgam containing about two parts of mercury to one part of copper, and then grinding together the carbon, the amalgain and the tungsten powder into a uniform mass in a mortar or similar device. This ground mass is then placed into a mold of the shape desired for the brush or the electrode and exposed to a very high pres-- sure, by hydraulic or other means, of about twenty to forty tons per sq. inch. Under this pressure, the mercury is.almost completely pressed out of the cracks or" the mold and can be collected in its pure state and used over again. The remaining" cake is then slowly heated to a temperature of about 300 degrees to 400 degrees C. which heating may be done in the open air. I have, however, found it preferable to first heat the cake below red heat in air and then to carry out and continue the heating process in vacuum or in anfinert atmosphere, to prevent oxidation and to facilitate the driving off of the last traces of mercury remaining after the compression.

After theheating, the cake consists of a solid piece of a mixture of either carbon and tungsten, copper and tungsten or carbon tungsten and. copper and is at once ready to be used as an electrode or as a brush in an electric machine.

y ired hardness may be obtained by & rial of binding qualities all var in the amounts of tunrsten co er or tric machinery or whatever mercury and by varying also the pressure applied When the mixture is being molded.

Instead of using an amalgam, I have found that I can use most any other matewhich can be volatilized without leaving any foreign traces in the perfected cake or composition. I can also use many organic binders which carbonize, thereby changing slightly the percentage'of the carbon in the finished prod.- ucts. A very good inorganic binder is cadmium-bismuthamalgam, but l have found that even water alone can be used with good success. As organic binders, I have found very useful alcohol, glycerin, sugar-syrups, gum-tragacanth solution, starch solution, collodium and others. When using; the cadmium-bisinuth-amalgam mixed. with copper, 'arbon and tungsten or carbon and tiringsten alone, after the pressing operation, the mercury as well as the bismuth and cadmium are volatilized by heat in hydrogen or in an inert atmosphere or in vacuum.

When using the organic binders above mentioned, or an inorganic binder such as water, these binders can be completely vola tilized after the compression, leaving the carbon, copper and tungsten product or the carbon and tungsten product depending upon the material used in the mixture.

The cakes comprising my improved composition of matter are molded into shapes for use as electrodes, or as brushes in elecform desired as above described.

narrate pressed mixturecontaining powdered tungsten.

6. An, electric contact consisting of a compressed mixture of carbon, copper and tungsten.

7. The process consisting of mixing carhon, copper amalgam and tungsten, subjecting the mixture to a high pressure and volatilizing the remaining mercury.

8. The process consisting of mixing a binder with carbon, copper and tungsten, subjecting the mixture to a high pressure, and volatllizing the binder.

In witness whereof I have hereunto set my hand at the borough of Manhattan, city and State of New York, this tenth day of March,

ALFRED J. LIEBMANN. In presence of- ETHEL D. BARON, JOHN J. RANACAN. 

